In the field of flat panel display devices, in which 2D display devices have been mainstream, display devices capable of displaying three-dimensional images are attracting attention these days, and some display devices are now commercially available. Flat panel display devices in the future will be naturally required to be capable of three-dimensional display, and wide studies are being conducted on flat panel display devices capable of three-dimensional display.
In order for a flat panel display device to display a three-dimensional image, it is generally necessary to display a right-eye image and a left-eye image separately to a viewer in some way. A so-called passive method, for example, is known as a method to separately display a right-eye image and a left-eye image. Three-dimensional display by the passive method will now be described with reference to FIG. 29. FIG. 29 is a schematic view illustrating three-dimensional display device as performed by the passive method. As shown in FIG. 29, the pixels of a flat panel display device are divided pattern-wise into two groups, right-eye image display pixels and left-eye image display pixels; the former group of pixels is caused to display a right-eye image, while the latter group of pixels is caused to display a left-eye image. The right-eye image and the left-eye image are converted into circular polarized lights by using a linearly polarizing plate and a patterned retardation film having a retardation layer formed in a pattern corresponding to the pattern in which the pixels are divided. The viewer wears circular polarization glasses, respectively adapted for the right eye and the left eye, so that the right-eye image reaches only the right eye and the left-eye image reaches only the left eye. The passive method can thus display a three-dimensional image to the viewer.
The passive method has the advantage that the use of the above-described patterned retardation film and circular polarization glasses can easily display three-dimensional images.
JP 2010-152296A discloses a method for producing a patterned retardation film by bringing an alignment film-forming layer into contact with a roll mold having a three-dimensional surface pattern which has been formed with a laser, thereby producing a shaped patterned alignment film having a pattern of a fine three-dimensional structure in the surface. JP 2010-152296A also describes a method for forming a pattern of a fine three-dimensional structure by polishing in the same plane.
However, such a patterned retardation film, produced by using a mold having a three-dimensional surface pattern which has been formed with a laser, has the following problem: defective alignment, i.e. disorder in the alignment direction of a liquid crystal compound, is likely to occur around the boundary between adjacent right-eye and left-eye regions in the patterned retardation layer, i.e. around the boundary between adjacent regions with different alignment directions of the liquid crystal compound, i.e. around the boundary between a first retardation region and a second retardation region. Thus, defective alignment may occur in the liquid crystal around the above-described boundary when the film is used in a liquid crystal display device. The defective alignment causes leakage of light from the boundary area, resulting in low-contrast images. When producing a fine three-dimensional structure with a laser, the fine three-dimensional structure is produced in a one-by-one manner. It therefore takes a considerable time to form the fine three-dimensional structure, having a size on the order of tens of nm or hundreds of nm, over a large area (e.g. of the size of an LCD TV). Further, the production of the fine three-dimensional structure requires the use of an apparatus for precisely controlling machining of the structure with the pitch of the asperities, which is on the order of tens of nm or hundreds of nm.
The lower limit of line width in machining of fine three-dimensional structures with a laser is generally at the level of hundreds of nm; machining with the line width at the level of tens of nm is difficult. Thus, it is generally difficult to produce a patterned alignment film having an excellent alignment regulating ability. In addition, there is the problem of the expensiveness of a laser machining apparatus.
JP 2010-152296A describes the producing of a mold by the use of a polishing method. When forming a three-dimensional pattern on the same plane by the polishing method of JP 2010-152296A to produce a roll mold, it is necessary to carry out polishing for each of patterning regions, each having a size of hundreds of nm, and to combine the patterned regions where fine three-dimensional structures have been formed. The method disclosed in the reference thus involves a complicated process which necessitates a considerable amount of time for machining and a high-accuracy operation.